The present invention relates in general to physical rehabilitation and exercise apparatus, and more particularly to physical therapy and exercise apparatus that provide both phasic and tonic exercise to a muscle group.
There are many exercise devices that are used to strengthen muscles of the lower or upper extremities. In regard to the legs, it is important to find exercises for increasing strength in functional weight-bearing tasks such as walking, running and jumping, while minimizing the damage to joints that may occur with repetitive training of these tasks. Currently available bicycle ergometers, although providing a good exercise for minimizing joint loading stress, all involve some seating mechanism that absorbs most of the body weight, such that weight-bearing on the exercised extremities is minimized.
One device, the cardiac stress table disclosed in U.S. Pat. No. 4,372,551, was developed to aid in the diagnostic imaging of the heart during different levels of cardiac stress. This device can tilt an individual about the approximate hip center and uses a shoulder pad system to retain the trunk in selected tilt positions. The device uses seated pedaling and therefore does not place significant tonic loads on the legs.
The victims of stroke and other medical conditions often lose much of their ability to retain their balance. Vertical sway is an indication of the user""s ability to control his or her center of mass during movement and is an important indicator of balance difficulties. According to conventional testing, sway tests are performed on a patient while the patient stands on a force platform. However, research indicates that these tests are poor predictors of falling behavior during locomotion, because they test individuals during quiet standing and not during movement.
Even in view of these and other prior art physical therapy and test apparatus, therefore, a need exists for physical therapy and exercise equipment that can effectively combine tonic with phasic exercise of muscle groups, such as occur in the legs and arms, and a further need exists for improved testing and treatment of balance disorders that result in falls during locomotion.
According to one aspect of the invention, physical therapy or an exercise apparatus is provided that provides both tonic and phasic exercise of preselected muscle groups, and in particular the muscle groups in the arms or legs of a user or patient. The invention includes first and second patient extremity contact surfaces, such as pedals or handgrips, which are rotatably mounted to a frame so as to define phasic exercise paths. The pedals/handles are coupled to a suitable source of resistance, such as a flywheel; it is preferred that the amount of resistance experienced by the user in performing the phasic activity be constant. A sled or torso carrier is slidably coupled to a frame and is movable in a path towards and away from the pedals/handles. The sled is biased toward the pedals/handles by a force, selectable in amount by the user or therapist, such that the muscle group being exercised receives a predetermined tonic load.
In one embodiment, the weight of the patient""s body itself is used to bias the torso carrier toward the pedals/handles; the patient must work to support the torso so as to be substantially constantly spaced from the pedals/handles, while at the same time performing a phasic muscle activity (such as advancing a crank). To select the amount of body weight which tonically loads the exercised extremities, the sled frame or track is tilted by an amount preselectable by the user around a pivot with respect to the rest of the frame. In other embodiments, the biasing is provided by springs or elastic bands. In yet another embodiment, this tonic loading is provided by a system of pulleys and weights. degree of movement of the sled may be fed back to the user, as by means of a visual display. The objective of the user is to keep the sled as stationary as possible while doing the phasic muscular exercise.
One technical advantage of the invention is that the tonic, or supportive, loading created by the ergometer adds an extra degree of muscle activity that becomes an effective stimulus for strengthening the muscles of the leg or arm. This extra degree of muscle strengthening occurs in muscle groups and with muscle actions that typically are not used during pedalling.
The main physiological effect during phasic exercise is the repetitive and sequential activation of muscle during the shortening and lengthening phases of the cycle. Typically, exercises are performed that focus on either lengthening or shortening contractions. The present invention heightens this effect by adding more loading to the activity. In embodiments provided to exercise the legs, the present invention advantageously trains the muscles of the legs to perform the kind of sequential eccentric and concentric contractions that occur in many daily locomotive activities.
Another advantage of the invention is that it is a closed-chain kinetic exercise. Open-chain exercises are potentially dangerous to the affected joints and muscles because they may put undue stress on these anatomical structures. In closed-chain exercises, such as those employed by the invention, the distal segment of the extremity is stabilized so that stresses on the exercised extermity are reduced. Closed-chain exercises are safer and more functionally relevant than the class of open-chain, isokinetic devices that are conventionally used to strenghten the legs and arms.